Portion of glass appears opaque in render
I would say it is just coincidence. The upper part is shadow casted by outside wall. It looks solid for several reasons. Partly because rendering this glass is very noise and thanks to denoising it just looks like flat (even more with your contrasted image).

When rendering in viewport without denoising, it looks also solid but with some more details.

As you already discovered - two &quot;Table Lights&quot; do some difference in render, even they are far and with very low power (just 10W and 60 W). Here rendered without those lights.

With those lights the render is significantly darker ... that is weird and I don't have an explanation for that, just theory.
Left render with two Point lights / Right render without ...

With provided file I didn't get such solid thing for final render with 240 samples.
Left render with two Point lights / Right render without ...

There is a difference in light rays bouncing, so it can be possibly caused by Render Properties &gt; Light Paths &gt; Clamping &gt; Indirect Light.
Also you are using Limited GL preset so try to increase Max Bounce for Diffuse to 8. With those changes the render seems to be same brightness also with the two Point Lights.